Because the emerging impacts of global warming such as more frequent extreme weather events can be explained in various ways, most people rely on the media for their information about global warming and the extent to which it is happening and its future consequences. In many cases it is their sole source of information.

Global warming is an issue that is often framed as a debate or controversy rather than as an environmental problem. Denial scientists are given more media exposure than their numbers or authority would normally warrant. And the media plays a major role in disseminating reports and expert views emanating from conservative think tanks that are seeking to cast doubt on global warming and downplay its impacts.

It is no accident that audiences of the more conservative media outlets, such as those owned by Rupert Murdoch's News Corporation (e.g. Fox News), have more doubts about the whether global warming is or will happen, and they are increasing over time. It reflects editorial policy and ultimately the owners ideology and/or vested interest with respect to government action to reduce greenhouse gas emissions.

Balance

Journalistic objectivity has two components. The first is ‘depersonalisation’ which means that journalists should not overtly express their own views, evaluations, or beliefs. The second is ‘balance’ which involves presenting the views of representatives of both sides of a controversy without favouring one side.

Balance means ensuring that statements by those challenging the establishment are balanced with statements by those whom they are criticising, though not necessarily the other way round. But giving equal treatment to two sides of an argument can often provide a misleading impression. By promoting global warming deniers, business takes advantage of the media's need for balance, and consequently the debate appears to be evenly divided even though the vast majority of climate scientists support the global warming consensus and there are only a handful of scientists disputing it. Phil Shabecoff, former environment reporter for the New York Times, gives the example of views on climate change:

the findings of the International Panel on Climate Change—a body of some 200 eminent scientists named by the World Meteorological Organization of the United Nations Environment Program—is generally considered to be the consensus position. But I have seen a number of stories where its conclusions are given equal or less weight than those of a single scientist who has done little or no significant peer-review research in the field, is rarely, if ever, cited on those issues in the scientific literature, and whose publication is funded by a fossil-fuel industry group with an obvious axe to grind.... for a reporter, at this stage of the debate, to give equal or even more weight to that lonely scientist with suspect credentials is, in my view, taking sides in the debate.

A study of the coverage of global warming between 1988 and 2002 in the prestige press in the US, that is the New York Times, the Washington Post, the Los Angeles Times, and the Wall Street Journal, found that the majority of stories, rather than reflecting the growing scientific consensus behind it "gave 'roughly equal attention' to the view that humans were contributing to global warming, and the other view that exclusively natural fluctuations could explain the earth's temperature increase".

Fox News' coverage of global warming even gave preference to the few global warming deniers. One analysis of content in 2007-8 found:

content analyses have shown that conservative media consistently claim a lack of scientific consensus on the reality of anthropogenic climate change... Studies have also found that Fox News [owned by Rupert Murdoch's News Corporation] airs significantly more stories that question the existence of human-caused climate change than stories that accept these scientific claims.
In turn, survey and experimental research have found relationships between exposure to these information outlets and beliefs about global warming.

Because people are often not able to judge the merits of scientific arguments for themselves they rely on judgements based on trust and shared values.

In this context, different media outlets help to cue audiences as to whether a particular institution or set of institutional actors, such as scientists, share a person's values and are thus trustworthy. They do this directly by reporting on scientific developments and controversies, but also by framing scientists and scientific issues in a way that makes certain values salient. For example, by amplifying coverage of climate contrarians' claims regarding the reality and seriousness of anthropogenic climate change, Fox News and other American conservative media have served to marginalize scientists in general and climate scientists in particular.

The portrayal in the more conservative media outlets of climate change scientist as biased and only interested in attracting research funding, as well as attacks by denial scientists on the peer review system has been damaging to the trust that conservative people have in science. Consequently, trust in scientists amongst Republican voters in the US has been declining, and this is even more so for climate change scientists.